Optional support for borsh serialization

Cargo.toml

@@ -14,6 +14,11 @@ categories = ["data-structures", "no-std"]
 
 [build-dependencies]
 
+[dependencies.borsh]
+version = "1.2.0"
+optional = true
+default-features = false
+
 [dependencies.serde]
 version = "1.0"
 optional = true
@@ -49,7 +54,7 @@ debug = true
 debug = true
 
 [package.metadata.docs.rs]
-features = ["serde", "zeroize"]
+features = ["borsh", "serde", "zeroize"]
 
 [package.metadata.release]
 no-dev-version = true

src/array_string.rs

@@ -628,6 +628,28 @@ impl<'de, const CAP: usize> Deserialize<'de> for ArrayString<CAP>
     }
 }
 
+#[cfg(feature = "borsh")]
+/// Requires crate feature `"borsh"`
+impl<const CAP: usize> borsh::BorshSerialize for ArrayString<CAP> {
+    fn serialize<W: borsh::io::Write>(&self, writer: &mut W) -> borsh::io::Result<()> {
+        <str as borsh::BorshSerialize>::serialize(&*self, writer)
+    }
+}
+
+#[cfg(feature = "borsh")]
+/// Requires crate feature `"borsh"`
+impl<const CAP: usize> borsh::BorshDeserialize for ArrayString<CAP> {
+    fn deserialize_reader<R: borsh::io::Read>(reader: &mut R) -> borsh::io::Result<Self> {
+        let s = <String as borsh::BorshDeserialize>::deserialize_reader(reader)?;
+        ArrayString::from(&s).map_err(|_| {
+            borsh::io::Error::new(
+                borsh::io::ErrorKind::InvalidData,
+                format!("expected a string no more than {} bytes long", CAP),
+            )
+        })
+    }
+}
+
 impl<'a, const CAP: usize> TryFrom<&'a str> for ArrayString<CAP>
 {
     type Error = CapacityError<&'a str>;

src/arrayvec.rs

@@ -1301,3 +1301,42 @@ impl<'de, T: Deserialize<'de>, const CAP: usize> Deserialize<'de> for ArrayVec<T
         deserializer.deserialize_seq(ArrayVecVisitor::<T, CAP>(PhantomData))
     }
 }
+
+#[cfg(feature = "borsh")]
+/// Requires crate feature `"borsh"`
+impl<T, const CAP: usize> borsh::BorshSerialize for ArrayVec<T, CAP>
+where
+    T: borsh::BorshSerialize,
+{
+    fn serialize<W: borsh::io::Write>(&self, writer: &mut W) -> borsh::io::Result<()> {
+        let vs = self.as_slice();
+        <usize as borsh::BorshSerialize>::serialize(&vs.len(), writer)?;
+        for elem in vs {
+            <T as borsh::BorshSerialize>::serialize(elem, writer)?;
+        }
+        Ok(())
+    }
+}
+
+#[cfg(feature = "borsh")]
+/// Requires crate feature `"borsh"`
+impl<T, const CAP: usize> borsh::BorshDeserialize for ArrayVec<T, CAP>
+where
+    T: borsh::BorshDeserialize,
+{
+    fn deserialize_reader<R: borsh::io::Read>(reader: &mut R) -> borsh::io::Result<Self> {
+        let mut values = Self::new();
+        let len = <usize as borsh::BorshDeserialize>::deserialize_reader(reader)?;
+        for _ in 0..len {
+            let elem = <T as borsh::BorshDeserialize>::deserialize_reader(reader)?;
+            if let Err(_) = values.try_push(elem) {
+                return Err(borsh::io::Error::new(
+                    borsh::io::ErrorKind::InvalidData,
+                    format!("expected an array with no more than {} items", CAP),
+                ));
+            }
+        }
+
+        Ok(values)
+    }
+}